This invention relates generally to coating apparatus and, more particularly, to apparatus for coating optical fibers.
It is known to coat an optical fiber by passing the optical fiber through a coating chamber in which a coating material, such as a metal oxide, for example, tin oxide, impinges on the fiber. Specifically, the optical fiber travels in the lengthwise direction thereof through the coating chamber, while at least one spray jet coats the optical fiber with the coating material while the latter is in vapor form.
With such arrangement, however, there is a tendency for the vapor stream to produce a non-uniform coating on the optical fiber. This is particularly so at low flow rates, and in view of rapid cooling of the optical fiber. It has therefore been necessary to use higher flow rates of the vapor stream. This, however, results in disturbance of the optical fiber. Specifically, the higher flow rates result in turbulence, causing a disturbance of the optical fiber with a resultant non-uniform coating. The turbulence also may result in the undesirable introduction of air into the chamber, and the production of a swirling current or eddy currents, which also produce a non-uniform coating.